1. Field of the Invention
The present invention relates to a process control system.
Priority is claimed on Japanese Patent Application No. 2012-068041, filed Mar. 23, 2012, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Conventionally, in plants, factories, and the like (hereinafter collectively referred to simply as plants), process control systems are implemented which control various state quantities such as pressure, temperature, and flow amount in industrial processes, and a high level of automated operation is achieved. In a conventional process control system, as shown, for example, in FIG. 7 of Japanese Patent (Granted) Publication No. 439973, FIG. 1 of PCT International Publication No. WO 2005/050336 and FIG. 1 of United States Patent Application, Publication No. 2007/0078980, the constitution is one in which a plurality of sensors, such as flow gauges and temperature gauges, and actuators, such as valves, are directly connected to controllers, the controllers controlling the actuators in accordance with the results of detection by the sensors, in order to control the above-noted various state quantities.
Although a plant is often designed to have a life of approximately 30 years, because general-purpose electronic components are used in the various devices that form the process control system (the above-described controller, sensors, and actuators), the life of the devices is determined by the life of the electronic components, and is approximately 10 years. Whereas a sensor that has reached the end of its life can be individually replaced, because general-purpose electronic components are mounted in I/O cards, which are the interfaces in controllers, the life of controllers is limited to approximately 10 years, and the life of the process control system is also limited.
In this manner, because the various devices that make up a process control system have lives that are shorter than that of the plant, it is necessary to replace (reconstruct) the process control system before the plant reaches the end of its life. As shown in FIG. 1 of Japanese Patent (Granted) Publication No. 439973, FIG. 2 of PCT International Publication No. WO 2005/050336 and FIG. 2 of United States Patent Application, Publication No. 2007/0078980, the extension of the life of a process control system can be envisioned by adopting a constitution in which various devices making up the process control system are connected to the same network and in which the above-noted I/O cards are eliminated.
The various devices making up a process control system use general-purpose electronic components in parts other than the controller I/O cards. For this reason, even if it is possible to extend the life of the process control system by eliminating the I/O cards as described above, the process control system will ultimately need to be replaced.
With the dramatic advances in technological made in recent years, it can be thought that there is a great possibility that a new process control system will be developed before the plant reaches the end of its life. Even when new technology is to be adopted, the existing process control system in the plant needs to be replaced by a new process control system.
In this case, in order to replace the process control system, it is basically necessary to stop the plant for a long period of time. For this reason, it should be considered that the cost of replacing the process control system is not only the cost of replacing the various devices making up the process control system, but also the cost of lost revenue from products that could have been produced if the plant had not been stopped. If such costs are considered, it is desirable to be able to change or add devices, while maintaining compatibility and without replacing the existing process control system.